This invention relates generally to anchors for fasteners such as screws, and in particular to anchors adapted for insertion into holes through walls.
Walls made of a friable material, such as drywall, are generally not strong enough to retain screws, nails, or other such fasteners fastened directly to the walls. As a result, articles fastened directly to walls by screws are easily pulled from the walls.
Various screw anchors have been used to prevent screws from being pulled from such walls. Such an anchor is typically inserted into a hole in a wall and has an aperture for receiving a screw. The screw, as it is threaded through the aperture, urges a shank portion of the anchor outward and against the wall. Thus, the screw is securely fastened to the wall. A problem with such an anchor is that it is liable to fall out of the hole before the screw is inserted into the anchor. Nothing retains it in the hole before the screw is inserted. Any likelihood of the anchor falling out of the hole makes the anchor more difficult to work with--especially when the anchor is to be placed in a hard-to-reach location.
Another problem with such an anchor is that it generally cannot accommodate walls of different thicknesses. One size anchor can generally only accommodate one size wall. Therefore, a user might have to stock many sizes of anchors if he hopes to have the correct size when needed.
Another problem is that such an anchor can generally only accommodate a particular size hole in a wall. If the hole is of different size the user must use an anchor of correspondingly different size